This invention is directed to the method of preparing hydrophilic poly 2-hydroxyethyl methacrylate polymers and copolymers and to their use as pressure sensitive adhesives, hydrogels, and coatings.
The family of synthetic hydrogels includes polyacrylic acid, polyvinyl pyrrolidone, polyvinyl alcohol, polyacrylamide, poly hydroxybutyl acrylate, and poly 2-hydroxyethyl methacrylate. In this family of synthetic hydrogels, poly 2-hydroxyethyl methacrylate and poly hydroxybutyl acrylate are water insoluble polymers prepared from a water soluble monomer. The other polymers require crosslinking to form a hydrogel with water.
2-Hydroxyethyl methacrylate polymers are of interest because of their biocompatibility as evidenced by excellent performance in animal implant studies. The extensive use of 2-hydroxyethyl methacrylate polymers for contact lenses for the eyes illustrates the non irritating nature of the polymers.
Other than commercial use in contact lenses, 2-hydroxyethyl methacrylate polymers have had limited commercial success, used at low percentages only, because of the nature of the monomer. Industrial grade 2-hydroxyethyl methacrylate monomer contains a small amount of crosslinker impurity which can cause gel formation during solvent polymerization. The 2-hydroxyethyl methacrylate monomer is water soluble and the 2-hydroxyethyl methacrylate polymer is water insoluble which causes difficulty in emulsion polymerization employing a high portion of 2-hydroxyethyl methacrylate monomer. The preparation of 2-hydroxyethyl methacrylate polymer therefore generally requires the use of very pure and expensive monomer or a very extensive and expensive polymerization process.
Requirements of high quality inkjet coatings include clarity, water resistance, good ink absorption with quick drying, and low surface friction to enhance sheet feeding in inkjet printers. Typical inkjet coatings satisfy the requirements of water resistance, good ink absorption with quick drying, and low surface friction through the use of mixtures of polymers, or polymers with pigments, however, these mixtures are not clear.
U.S. Pat. No. 2,976,576 describes the use of poly 2-hydroxyethyl methacrylate resin for contact lenses and body implants.
U.S. Pat. No. 3,220,960 describes the use of poly 2-hydroxyethyl methacrylate resin for contact lenses and body implants.
U.S. Pat. No. 3,567,760 describes the preparation of 2-hydroxyethyl methacrylate copolymers in methanol that are water soluble salts for entrapping drugs, pesticides, flavoring agents, and fragrances.
U.S. Pat. No. 3,963,685 describes the preparation of methanol soluble poly 2-hydroxyethyl methacrylate for wound care dressings using high purity 2-hydroxyethyl methacrylate monomer having not over 0.035 weight percent of alkylene glycol dimethacrylate impurities.
EP 024164A1 describes the preparation of methanol soluble poly 2-hydroxyethyl methacrylate using high purity 2-hydroxyethyl methacrylate monomer.
Polymer International, vol. 36 no. 4, pp.303-308 (April 1995), describes the preparation of dimethylformamide soluble poly 2-hydroxyethyl methacrylate using a chain transfer agent to prevent gellation.
U.S. Pat. No. 4,303,066 describes the use of a plasticized poly 2-hydroxyethyl methacrylate resin prepared from high purity monomer as a non-tacky synthetic film for skin burns, with shortened forming time by adding water to the mixture.
U.S. Pat. No. 4,593,053 describes the use of a plasticized polyvinyl pyrrolidone as a hydrophilic medical type pressure sensitive adhesive for biomedical electrodes and transdermal devices.
WO 92/11825 describes the use of plasticized poly 2-hydroxyethyl methacrylate resin as a hydrophilic medical type pressure sensitive adhesive for a medical device.
U.S. Pat. No. 5,225,473 describes the use of a UV cured plasticized polyvinyl pyrrolidone as a hydrophilic medical type pressure sensitive adhesive for biomedical electrodes and transdermal devices.
U.S. Pat. No. 4,892,787 describes coated paper for inkjet printing containing pigment, an acrylic emulsion, and a water soluble polymer.
U.S. Pat. No. 5,206,071 describes acrylic graft copolymers and water soluble polymers.
U.S. Pat. No. 5,478,631 describes an inkjet recording sheet using a pigment and an amphoteric ion latex.
EP 0716929A1 describes acrylic graft copolymers and water soluble polymers.
DE 19516111A1 describes water soluble copolymers with crosslinkers.
U.S. Pat. No. 5,672,392 describes the preparation of recording materials for inkjet printers using acrylic emulsions and water soluble polymers.
The present invention is directed to providing a cost-effective method for the preparation of hydrophilic 2-hydroxyethyl methacrylate polymers and copolymers with utility as coatings and pressure sensitive adhesives.
The present invention is further directed to providing clear inkjet coatings without pigments that are water resistant and have good ink absorption with quick drying.
A method is provided for the preparation of gel-free poly 2-hydroxyethyl methacrylate substantially in the absence of a chain transfer agent, comprising introducing monomeric 2-hydroxyethyl methacrylate containing ethylene glycol dimethacrylate impurities in the range of no more than about 0.05-0.1% by weight of the monomer, into alcohol, polymerizing the 2-hydroxyethyl methacrylate to form a polymerization mixture, and optionally removing the alcohol. The alcohol is preferably selected from one of methanol and ethanol. Hydrophilic pressure sensitive adhesives are provided by adding polyethylene glycol to the polymerization mixture prior to removing the alcohol. Flexible hydrophilic coatings also are provided by adding glycerin to the polymerization mixture prior to removing the alcohol by drying.
In another embodiment, the monomeric 2-hydroxyethyl methacrylate contains alkylene glycol methacrylate impurities in the range of no more than about 3% by weight, wherein the alkylene glycol methacrylate impurities are selected from the group consisting of ethylene glycol dimethacrylate, diethylene glycol monomethacrylate, methacrylic acid and mixtures thereof.
A method is also provided for the preparation of a gel free, hydrophilic, water soluble polymer substantially in the absence of a chain transfer agent comprising a copolymer of 2-hydroxyethyl methacrylate and acrylic acid or methacrylic acid, including introducing monomeric 2-hydroxyethyl methacrylate into water solution with one of acrylic acid and methacrylic acid, adjusting the pH of the solution to a pH in the range of greater than about pH 3 to less than about pH 9, and copolymerizing the monomeric 2-hydroxyethyl methacrylate and acrylic or methacrylic acid.
In one embodiment, the monomeric 2-hydroxyethyl methacrylate contains at least 0.05% by weight, based on the monomer, of ethylene glycol dimethacrylate.
In another embodiment, hydrogels are prepared with copolymer concentrations greater than about 35% by weight.
In another embodiment, the copolymer of 2-hydroxyethyl methacrylate and acrylic acid or methacrylic acid is blended with a polyalkylene glycol, such as polyethylene glycol, to form a pressure sensitive adhesive.
In another embodiment, the copolymer of 2-hydroxyethyl methacrylate and acrylic acid or methacrylic acid is blended with glycerin to form a flexible coating.
A method is also provided for the preparation of a gel free hydrophilic polymer substantially in the absence of a chain transfer agent comprising a copolymer of 2-hydroxyethyl methacrylate and 4-hydroxybutyl acrylate, including introducing monomeric 2-hydroxyethyl methacrylate containing no more than about 0.05-0.1% by weight of ethylene glycol dimethacrylate into an alcohol solution with 4-hydroxybutyl acrylate, polymerizing the 2-hydroxyethyl methacrylate and 4-hydroxybutyl acrylate to form a polymerization mixture, and removing the alcohol. The alcohol is selected from one of methanol and ethanol, with ethanol being preferred.
In another embodiment, the monomeric 2-hydroxyethyl methacrylate contains no more than about 3% by weight alkylene glycol methacrylate impurities, wherein the alkylene glycol methacrylate impurities are selected from the group consisting of ethylene glycol dimethacrylate, diethylene glycol monomethacrylate, methacrylic acid and mixtures thereof.
A method of preparing an acrylic emulsion ink jet receptive clear coating is also provided comprising: forming an alkyl acrylate monomer-containing pre-emulsion feed mixture, introducing an activator into the alkyl acrylate monomer-containing pre-emulsion feed mixture, reacting a water soluble monomer feed in said alkyl acrylate monomer-containing pre-emulsion feed mixture, said water soluble monomer feed comprising 2-hydroxyethyl methacrylate and n-vinylpyrrolidone, to form a clear polymer in said alkyl acrylate monomer-containing pre-emulsion feed mixture.
In another embodiment, the method further comprises subsequently reacting with said clear polymer in said alkyl acrylate monomer-containing pre-emulsion feed mixture, a water insoluble monomer feed mixture comprising 2-hydroxyethyl methacrylate, n-vinyl pyrrolidone, butyl acrylate, and methacrylic acid to form a clear polymer over said polymer in said alkyl acrylate monomer-containing pre-emulsion feed mixture.
A method for the preparation of a powdered low gel poly 2-hydroxyethyl methacrylate substantially in the absence of a chain transfer agent is also provided comprising: introducing monomeric 2-hydroxyethyl methacrylate containing ethylene glycol dimethacrylate impurities in the range of no more than about 0.05 to about 0.1% by weight, based on the monomer, into water, polymerizing the 2-hydroxyethyl methacrylate, drying said polymerized the 2-hydroxyethyl methacrylate, and grinding said dried polymerized 2-hydroxyethyl methacrylate to form a powder.
In another embodiment, the monomeric 2-hydroxyethyl methacrylate contains no more than about 3% by weight alkylene glycol methacrylate impurities, wherein the alkylene glycol methacrylate impurities are selected from the group consisting of ethylene glycol dimethacrylate, diethylene glycol monomethacrylate, methacrylic acid and mixtures thereof.
In another embodiment, said poly 2-hydroxyethyl methacrylate powder is blended with a polyalkylene glycol, such as polyethylene glycol to form a pressure sensitive adhesive.
The term xe2x80x9clow gelxe2x80x9d as used in the specification refers to a poly 2-hydroxyethyl methacrylate (polyHEMA) polymer having less than 15% gel content, as determined by the method described hereinbelow.
The term xe2x80x9cgel freexe2x80x9d as used in the specification refers to a polyHEMA polymer having less than 5% gel content, as determined by visual inspection or by the xe2x80x9cgel contentxe2x80x9d method described hereinbelow. The presence of any gel in the polymeric product was determined by pouring a thin film of the product and visually inspecting for any particulate.
The xe2x80x9cgel contentxe2x80x9d of the poly HEMA polymers is a measure of the polymer that is insoluble in methanol (MeOH). The gel content is determined as follows: The poly HEMA adhesive polymer is coated onto a silicone release liner and dried at 70xc2x0 C. for 15 minutes. The adhesive is removed from the release liner, and a 60 to 80 mg sample of the adhesive is accurately weighed out and placed into a 10 xcexcm PTFE membrane filter. The edges of the filter are thermally sealed to contain the sample, and the filter is placed in a vial containing about 15 g of methanol. The vial is agitated for 72 hours, and the filter is taken out of the solvent and dried at 120xc2x0 C. for 120 minutes.
The filter is then weighed, and the resulting weight of the sample is used to calculate the percent gel as follows:
% gel=(b/a)xc3x97100
wherein,
a=initial weight of the sample, and
b=final weight of the sample.